of munich



Patented Aug. 4, 1931 UNITED STATES T N S] RUDOLF MEINGAST AND MARTIN MUGDAN, OF MUNICH, GERMANY, ASSIGNORS TO CONSORTIUM FUER ELEKTROCHEMISGHE INDUSTRIE, OF MUNICH, GERMANY PROCESS OF MANUFACTURING ACETIC ANHYDRIDE No Drawing. Application filed June 2, 1927, Serial No. 196,136, and in Germany June 16, 1926.

In carrying out the process of manufacturing acetic anhydride by heating acetic acid vapor to high temperatures, described for example in; U. S. Patent No. 1,570,514 it is important for the heat transmitting surfaces of the heating chamber to be constructed of such material which has not only no undesired decomposing effect on the vapor of acetic acid, but has also a high thermal conductivity. As

acetic acid vapor at temperatures of between 240 and 410 0., inclining especially to the formation of methane and carbon dioxide (Sabatier La Catalyse 2nd edition 1920, p. 328; Gmelin-Kraut, Handbuch der organ, Chemie, IV, Aufiage, Bd. X. S. 624). For this reason the U. S. Patent No. 1,570,514 for carrying out the process as far as it is performed without the use of catalysts prescribes c the absence of base metals.

The present invention relates to the appli cation of our discovery, that a number of base metals which, according to the statements in the literature cited above are said to have a strongly decomposing action on acetic acid vapor, are applicable as materials for the heating apparatus in' the, process in question. This is the case particularly with the acid resisting chromium-iron alloys such as duraloy of the Duraloy 00., Pittsburgh, containing about 30% chromium, trace of silicon and carbon, and iron by difference, and the alloys V2A, containing chromium, 7% nickel, carbon, iron by diflerence, VM and nichrotherm, similar steel alloys having from 10-25% chromium and from 410% nickel, iron by difference, made by Friedrich Krupp in Essen, Germany.

Emample 1501000 g. acetic acid vapor per hour are 50 water and the unchanged acetic acid. The

is known, the ordinary base metals decompose decomposition of the acetic acid in other directions is only very slight.

Eat-ample II The procedure is the same as in Example I, but the V2A-tube is filled with the aluminum phosphate catalyst described in U. S. Patent No. 1,570,514, Example VI. In this case. the condensed product contains 40-45 per cent acetic anhydride. The decomposition in by-products is again very unimportant. Ewample I I l 1. Process for preparation of acetic anhydride comprising heating acetic, acid FFlc-E Vapor to 400-800 C. on heat conducting surfaces composed of an alloy of chromium which does not decompose acetic acid at that temperature.

vapor in the presence of dehydrating catalysts to 400-800 C. on heat conducting surfaces composed of an alloy of chromium which does not decompose acetic acid at that temperature.

. 3. Process for the preparation of acetic anhydride comprising heating acetic acid vapor to 400800 G. on heat conducting surfaces composed of an alloy of chromium and iron containing 10 to 30% chromium.

4. Process for the preparation of acetic anhydride comprising heating acetic acid vapor in the presence of dehydrating catalysts to 400800 C. on heat conducting surfaces composed of an alloy of chromium and iron containing 10 to 30% chromium.

5. Process for the preparation of acetic anhydride comprising heating acetic acid vapor in the presence of a dehydrating catalyst to 400-800" C. on heat conducting surfaces composed of an alloy of chromium, iron and nickel, containing 1025% chromium and 4F1O% nickel! RUDOLF MEINGAST. MARTIN MUGDAN. 

